1. Field of the Invention
The present invention relates to biodegradable lubricants and greases.
2. Description of the Art
Biodegradable lubricants and greases are desirable because they provide an alternative to petroleum based lubricants which are toxic to the environment and which are increasingly difficult to dispose of safely and economically. Moreover, there has been an increasing demand for “green” lubricants in recent years due to increasingly strict government regulations controlling and restricting the use of traditional petroleum-based lubricants. Vegetable oils provide good alternatives because they are non-toxic, readily biodegradable, readily renewable, safe to handle, and environmentally friendly.
The triacylglycerol structure of vegetable oil, which is amphiphilic in character, accounts for its potential as an excellent candidate for use as a functional lubricant. Triacylglycerol molecules typically orient themselves with their polar ends making contact with any solid surface, becoming closely packed together and forming a surface film on the material being lubricated. In addition, the vegetable oil structure provides sites for various functional groups that permit the oils to be modified for improved technical properties such as thermo-oxidative and low temperature stability. These properties make vegetable oils very attractive for industrial applications that have potential for environmental contact through accidental leakage or through ordinary disposal.
The oil from castor seed (Ricinus communis) is particularly useful because it is extremely viscous and is therefore an excellent source for biodegradable lubricants and greases. Worldwide, the annual production of castor oil is about 460,000 tons (1.1 million tons of seeds) produced mainly in India, Brazil and China (http://www.hort.purdue.edu/newcrop/). The U.S. spends over $50 million annually to import castor for industrial applications including such diverse products as lubricants, greases, plasticizers, cosmetics, pharmaceuticals, paints, plastics, coatings, antifungal compounds, shampoo, and thermopolymers. Conventional domestic production of castor oil, however, is seriously hindered due to the presence of a toxic protein, ricin, as well as various allergenic albumins.
The usefulness and versatility of castor oil is due to the fact that approximately 90% of the fatty acid composition in castor oil is ricinoleic acid, an hydroxyl fatty acid, which is naturally present in few other plants and then only in small amounts.
Currently, one of the major issues in plant biotechnology is the elucidation of how plants assemble various compounds and specifically how to isolate and purify such compounds, particularly when they have useful industrial applications such as ricinoleate. In plant lipid metabolism, for example, it is possible to isolate various genes which can then be manipulated for the purpose of altering fatty acid composition. Manipulation of how these genes operate underlies future progress in developing crops containing high levels of hydroxylated fatty acids.
In fact, there have already been attempts to produce and extract ricinoleate from transgenic plants which do not produce the noxious components incident to castor oil production. These efforts have focused on plants such as tobacco and Arabidopsis, and have been mostly directed to the expression of a cDNA encoding fatty acyl hydroxylase (FAH), an enzyme catalyzing the hydroxylation of oleate to ricinoleate in castor. Only low levels of hydroxy fatty acids have been achieved using this approach, however, which suggests that the FAH gene itself is not sufficient to produce the high level of ricinoleate characteristic of castor.
A more productive approach, therefore, is necessary.